The Herpes viruses are responsible for many human diseases. All Herpes viruses possess a proteinaceous layer termed tegument which lines the inner surface of their envelope. Correct assembly of tegument and envelope is essential for the production of an infectious viral particle, and thus for the progression of disease. However, little is known of how tegument proteins recognize and bind to specific cellular membranes, nor how they ensure their assembly into the maturing virion. The first part of this proposal will investigate the biochemistry of the Herpes simplex virus (HSV) protein vhs, a component of the HSV tegument. We have previously identified several biochemically distinct forms of vhs in infected cells. We will now investigate the relationship between these molecules and determine their importance for assembly of vhs into tegument. Next, we will dissect the molecular mechanism by which vhs binds to intracellular membranes. Finally, we have successfully isolated primary enveloped HSV particles from the perinuclear space. We will study the composition and function of tegument in these HSV assembly intermediates.